Introduction to TrREXS

By employing free-electron lasers as a new generation of light sources, ultrashort pulses and high intensity are used to achieve time-resolved resonant elastic X-ray scattering (TrREXS) measurements. Selective excitation of ordered electronic states in correlated systems is performed using pump sources such as infrared lasers, revealing the interactions and ultrafast dynamics between ordered states and collective excitations across various degrees of freedom in correlated materials.